On gold and silver metallics, I think clarity and reflection are the most desireable characteristics. In that case, EX-P would be a great choice. Like Scott mentioned, 4*UPP is a great choice too. I just recently did a side by side comparison on my hood with EX-P and 4*UPP on the other side. UPP is not quite as clear and reflective as EX-P but it defnitely looks like it has more depth. On my silver metallic TL, it's the one that has best given me the look I want.
Wolfgang will definitely mute the flakes in metallic paint. It has a very *soft* look to it. I really like it on black. Some of the more clear LSP's (like EX-P and Zaino) are very clear but it tends to make black look like a mirror and washes out a lot of depth. WG is very glossy and wet looking on black... a great choice for darker colors.
I do have to mention that while I like most everything I tried in the WG line, I don't like the pre-cleaner. It's not that it's that bad... just in IMHO there are a lot better products out there for that stage (VM comes to mind.)